| 英文摘要: | Interactions between soil microbes, the physical soil environment and vegetation will determine the magnitude of the terrestrial carbon sink under climate change. Accurate carbon cycle projections are needed to inform climate change adaptation and mitigation strategies. Such projections require understanding of biological responses to environmental change, especially in the world beneath our feet. Globally, soils store more carbon than plants and the atmosphere combined. Soils also provide habitat for a stunning diversity of organisms that are largely responsible for the stabilization and decomposition of soil carbon. Writing in Nature Climate Change, Sulman et al.1 present a fresh look at how soil microbial activity can be simulated at global scales and illustrate why such considerations matter. Their findings underscore the need to explicitly incorporate soil microbial response to environmental change in soil biogeochemical models. Environmental change effectively reshuffles the deck of biological rules that determine how ecosystems function. Most current soil biogeochemistry models that are applied at ecosystem to global scales do not specifically consider soil microbial activity and so fail to represent the 'reshuffling' effect2. This raises concerns about the accuracy and certainty of the soil carbon projections derived from these models. Mounting evidence suggests that plants and soil microbes respond in unexpected ways to a variety of perturbations such as changing climate, land use and nitrogen load. For example, increased concentrations of CO2 in the atmosphere change how and where plants use carbon for growth3. In many ecosystems, carbon–nitrogen interactions modulate plant and soil responses under increased CO2 (ref. 4). These interactions directly influence soil microbial activity in ways that could attenuate potential gains in terrestrial carbon storage in a CO2-rich world5. By omitting these insights, current models potentially misrepresent critical changes in the largest terrestrial carbon pool on Earth. The work presented by Sulman and colleagues1, therefore, marks an important development that could help to advance our understanding of the mechanisms that influence soil functioning. Their new model, Carbon, Organisms, Rhizosphere, and Protection in the Soil Environment (CORPSE), explicitly considers interactions between soil microbial activity and the physical soil environment. Microbial activity is simulated for bulk soil and for soil near fine roots, referred to as the rhizosphere (Fig. 1). Rhizosphere soils are characterized by accelerated microbial activity because they receive additional inputs of easily decomposed carbon supplied by fine roots. Experimental work demonstrates that increased CO2 increases the volume of rhizosphere soils, thus accelerating the decomposition of soil organic matter6. Evaluation of the applicability of these findings is necessary to quantify the broader importance of rhizosphere dynamics across systems, but they present tantalizing new insight into unexplored aspects of the terrestrial carbon cycle.
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